FUNCTIONAL SYSTEMS OF THE BODY
The article describes a brief description of several functional systems of the body, such as the cardiovascular system, nervous system, muscular system, skeletal system and anterior system.
FUNCTIONAL SYSTEMS OF THE BODY
The cardiovascular system.
Homeostasis – constancy of the internal environment of the body.
Blood and circulatory system. Blood is a liquid tissue that circulates in the circulatory system, ensuring the vital activity of cells and tissues of the body. The composition and properties of blood in an adult are constant (but change during illness). The constancy of the blood composition is maintained by the physicochemical mechanisms of the blood itself and the regulatory mechanisms of the nervous system. Blood consists of a liquid part - plasma (55–60%) and cellular elements suspended in it (40–45%) - erythrocytes, leukocytes, platelets.
Erythrocytes are red blood cells filled with a special protein - hemoglobin, which causes the red color of blood. The most important function of red blood cells is that they are oxygen carriers.
Leukocytes - white blood cells - perform a protective function: they have the property of phagocytosis, that is, they capture and destroy pathogenic microbes and proteins foreign to the body.
Platelets (blood platelets) are cellular elements that play an important role in the process of blood clotting. Under normal conditions, blood moving through the vessels does not clot. Only in certain diseases do blood clots, thrombi, form inside the vessels and clog them. Blood clotting usually occurs when the body and blood vessels are damaged.
Plasma is the intercellular substance of blood. Plasma consists of 90% water and 10% other substances. In addition to cellular elements, plasma contains blood proteins, various nutrients (amino acids, glucose, etc.), hormones, enzymes, carbon dioxide and oxygen, metabolic products removed from tissues.
Plasma contains antibodies that provide immunity to the body.
Blood in the body performs many functions:
- transport – delivers nutrients (fatty acids, amino acids, etc.) to the tissues of all organs and removes breakdown products (uric acid, ammonia, etc.) from there. Nutrients enter the bloodstream by being absorbed in the digestive system. Decay products formed as a result of cell activity are removed from the blood through the excretory organs;
- respiratory - delivers oxygen to the tissues of all organs and removes carbon dioxide from there. The entry of oxygen into the blood and the removal of carbon dioxide from the blood occurs through the lungs;
- regulatory – carries various substances (hormones, etc.) throughout the body that enhance or inhibit the functioning of organs. For example, adrenaline secreted by the adrenal glands causes faster and stronger contractions of the heart, narrows the lumen of blood vessels (except for those of the heart and brain), thereby increasing blood pressure;
- protective – prevents the action of harmful substances, bacteria, foreign particles penetrating into the body;
- heat exchange – ensures a relatively uniform distribution of heat in the body. Passing through organs with a high level of metabolism (for example, the liver), the blood heats up, simultaneously cooling them, then, passing through organs with a low level of metabolism (for example, the skin), it cools, while simultaneously warming them.
During regular exercise or sports:
- the oxygen capacity of the blood increases, as the number of red blood cells and the amount of hemoglobin in them increases;
- the body’s resistance to various diseases increases due to increased activity of leukocytes;
- recovery processes are accelerated after significant blood loss.
Circulatory system. The circulatory system consists of the heart and blood vessels - tubes of various diameters, sequentially connected to each other and forming closed large and small circles of blood circulation. The circulatory system contains blood. The blood in the body is in constant motion, which occurs through the blood vessels. This movement is called blood circulation. Blood circulation ensures a continuous flow of nutrients and oxygen to all organs and the removal of metabolic products from them. The movement of blood in the vessels occurs due to contractions of the heart.
The human body is penetrated by blood vessels, and they do not end anywhere, but pass into each other and form a single closed system. Blood vessels are divided into arteries, arterioles, veins, venules and capillaries. Arteries are vessels through which blood flows from the heart to the organs. In organs, the arteries are divided into smaller ones (arterioles), and then into the smallest blood vessels - capillaries. Capillaries are the most numerous and thinnest blood vessels. Capillaries are connected to each other, forming capillary networks. There are arterial and venous parts of the capillary. The venous parts of the capillary form capillary venules, which collect into veins.
The exchange of substances between blood and tissues occurs only through the walls of capillaries. Veins are vessels through which blood flows from organs to heart.
Valves present in many veins ensure that blood flows in one direction. Particularly important is the presence of valves in the veins of the lower extremities. The same purpose is served by the “muscle pump” - a mechanism for forced movement of blood under the influence of contraction and relaxation of skeletal muscles. All blood vessels in the human body make up two circles of blood circulation - large and small.
The network of vessels of the systemic circulation permeates the tissues of all organs and parts of the human body. The systemic circulation refers to the path of blood from the left ventricle of the heart through the aorta - the largest arterial vessel - and its branches to the organs and from the organs through the venous vessels to the right atrium, and from it to the right ventricle. In the systemic circulation, blood turns from arterial to venous.
The pulmonary vasculature passes only through the lungs. The pulmonary circulation serves to enrich the venous blood flowing from the organs with oxygen and remove carbon dioxide from it. The pulmonary circulation is the path of blood from the right ventricle of the heart through the pulmonary artery to the lungs, where the blood releases carbon dioxide and is saturated with oxygen, and from there through the pulmonary veins to the left atrium, and from there to the left ventricle, and the circulatory cycle repeats. In the pulmonary circulation, blood turns from venous to arterial.
In addition to the blood vessel system, the human body has a lymphatic system. The lymphatic system is an additional (along with the venous bed) link for the outflow of fluid and substances dissolved in it from organs and tissues.
Blood circulating in the vessels exerts a certain pressure on their walls. Under normal conditions, blood pressure is constant. During ventricular systole, blood pressure is higher than during ventricular diastole. Therefore, a distinction is made between maximum, or systolic, blood pressure and minimum, or diastolic, blood pressure. Blood pressure is measured at the brachial artery and is therefore called blood pressure (BP). Pulse pressure is the difference between maximum and minimum blood pressure.
Physical activity contributes to the general expansion of blood vessels, increasing the elasticity of their walls, and improving metabolism in them. The muscles surrounding the vessels massage their walls. The blood vessels of the brain, skin, and internal organs that do not pass through the muscles are massaged due to the hydrodynamic wave from the increased heart rate and due to the accelerated blood flow. But as a result of exercising with an excessive increase in load, a negative effect can occur.
Heart function indicators. As a result of systematic exercise and sports, the size and weight of the heart increases due to the thickening of the walls of the heart muscle and an increase in its volume. The blood supply to the heart itself improves, and therefore its nutrition. Such changes increase the power and efficiency of the heart.
Heart rate (HR), or arterial pulse, is a very informative indicator of the performance of the cardiovascular system and the entire body. The pulse is a wave of oscillations propagated along the elastic walls of the arteries as a result of the hydrodynamic shock of a portion of blood ejected into the aorta under high pressure during the contraction of the heart.
A slower heart rate in trained people provides the heart with a longer pause to rest.
The main functional features of the circulatory system of people who systematically engage in physical exercise are high efficiency of functions at rest (for example, a decrease in heart rate) and when performing loads below the maximum; high performance of the circulatory system when performing maximum loads. In general, the cardiovascular system of a trained person has a greater margin of safety.
Nervous system. The nervous system regulates all the activities of the body and communicates with the external environment.
Functions of the nervous system:
- regulates the activity of various organs and the whole body - the work of muscles, heart, secretion of glands, metabolism, etc.;
- communicates between different organs and systems, coordinates their activities, determining the integrity of the body;
- communicates the body with the external environment: all irritations coming from the external environment are perceived by the senses;
- processes occurring in the cerebral cortex underlie mental phenomena - thinking, speech, memory, attention, perception of the surrounding world, volitional manifestations, emotions, etc.
The main condition for the normal existence of an organism is its ability to quickly adapt to environmental changes. This ability is provided by the nervous system. At the same time, the activity of the nervous system is aimed at maintaining homeostasis - the constancy of the internal environment.
The nervous system is conventionally divided into central and peripheral. The brain and spinal cord make up the central part of the nervous system, the central nervous system (CNS). The structural and functional unit of the nervous system is the nerve cell (neuron).
With systematic physical training, higher nervous activity (cerebral cortex) and the functions of the nervous system are improved. The interaction of the processes of excitation and inhibition of various nerve centers is carried out more subtly. The functions of analyzers are improved. The ability to learn new movements and improve existing ones develops. Physical training has a diverse impact on mental processes, ensuring their activity and improvement. Physical training contributes to the development of strong-willed personality traits - determination, courage, determination, endurance, etc.
Respiratory system. Gas exchange constantly occurs between the body and the environment - the exchange of gases between the outside air and the blood. Gas exchange (breathing) is a function of the respiratory system. The respiratory system consists of airways - the nasal cavity, pharynx, larynx, trachea, bronchi and the respiratory part - the lungs.
There are external (pulmonary) and intracellular (tissue) respiration.
The lungs are located in a hermetically sealed chest cavity (cage). The exchange of air in the lungs occurs as a result of respiratory movements of the chest. The main respiratory muscles are the diaphragm and intercostal muscles.
Systematic exercise and sports strengthen the respiratory muscles, increase the volume and mobility (excursion) of the chest, increase the capillary network in the lungs, etc.
Indicators of the respiratory system: tidal volume, respiratory rate, minute respiratory volume (MRV), vital capacity (VC), maximum oxygen consumption (MOC).
Systematic physical training, improving the respiratory and circulatory systems, increasing the hemoglobin content, the rate of oxygen release from the blood, etc., significantly expands the body’s ability to consume oxygen, thereby delaying the onset of hypoxia (oxygen starvation).
Skeletal system. The skeletal system consists of bones connected to each other in various ways and forming the skeleton - the solid support of the human body, which determines its shape. The skeleton protects internal organs from external influences. For example, the brain is located in the cranial cavity, the spinal cord is located in the spinal canal, and the heart and lungs are located in the chest. The skeleton is the passive part of the musculoskeletal system.
Bone is a complex organ. Each bone is supplied with nerves, blood and lymphatic vessels, and contains bone marrow.
Skeletal structure:
- torso – spinal column and chest;
- head – skull;
- upper limbs;
- lower limbs.
Through systematic exercises you can increase the degree of joint mobility. Then, under conditions of normal physiological activity and motor activity, the joints will maintain their range of motion longer and undergo aging more slowly. Physical labor and sports contribute to the development of more advanced mechanical properties of the bone - greater resistance to fracture, compression, stretching, and torsion. Excessive physical activity negatively affects the structure and function of joints, leading to mobility limitations and a decrease in range of motion. A sedentary lifestyle, insufficiently developed and untrained muscles adversely affect the spine: physiological curves increase, the strength of intervertebral ligaments weakens, intervertebral discs become deformed, and there is a risk of lateral curvatures (scoliosis). Physical exercises have a great influence on the development of the spinal column, preventing the development of stoop, pathological lateral curvatures, and are also a powerful means of correcting existing defects. Systematic physical exercise, especially strength and speed-strength exercises, stimulate bone remodeling. Bones that experience the greatest load become more massive and stronger. Bone aging slows down.
Muscular system. Depending on the structure and functional characteristics, striated, smooth and cardiac muscles are distinguished.
The composition of striated muscles includes striated muscle tissue. These muscles contract at the will of the person (voluntarily). This group includes skeletal muscles (head, torso, limbs) and muscles of some internal organs (tongue, larynx, etc.). Skeletal muscles constitute the active part of the musculoskeletal system.
Smooth muscles consist of smooth muscle tissue and are found in the walls of hollow internal organs (stomach, intestines, bladder, etc.) and blood vessels. The contraction of these muscles determines the volume of organs, the size of their lumen, as well as the movement of the contents of internal organs (for example, food in the digestive canal). The contraction of smooth muscles does not depend on the will of a person (they occur involuntarily).
The heart muscle contracts involuntarily, but is formed by striated muscle tissue of a special structure.
The structural and functional unit of skeletal muscle is the muscle fiber. Muscle fibers are united into bundles. Each muscle consists of many such bundles. Individual muscle bundles and the entire muscle have a thin membrane.
The main functions of muscles include movement, holding the body, and protecting internal organs.
Myofibrils (contractile filaments), contained in muscle fibers and stretching from one end of the muscle fiber to the other, ensure their contraction. The muscle fibers are parallel to each other, so the force of the contracting muscle fibers is additive.
Physical training is also accompanied by the improvement of the nervous mechanisms for regulating muscle activity. Such changes increase muscle strength and endurance, which has a beneficial effect on the entire body, since changes simultaneously occur in all other systems and organs.